The file is just a Java JAR file - so you need a copy of Java Version 1,6 or above installed on your machine.

Try double clicking the file to run it as some operating systems know what to do with them. If that doesn't work then it can be run using: java -jar WebbotDownload.jar

When run you will see some error icons - but that's normal !! It's because it doesn't know where you want to download the files to. Double click on an entry and set the folder to where you want it stored. It will then start downloading.

Once an entry has been set up then it will automatically download new versions if you are connected to the internet.

But don't panic: for the WebbotLib download it will store each release into a new sub-directory just in case you want to carry on using an older version.